Field of the Invention
The present invention relates to a technique for predicting the meandering of an elongated strip-shaped base material in a processing position lying on a transport path in a base material processing apparatus for processing the base material while transporting the base material.
Description of the Background Art
An inkjet image recording apparatus which records an image on elongated strip-shaped printing paper by ejecting ink from a plurality of recording heads while transporting the printing paper has heretofore been known. In the image recording apparatus of this type, inks of different colors are ejected from the respective recording heads. A multi-color image is recorded on a surface of the printing paper by superimposing single-color images formed by the respective color inks. The image recording apparatus of this type includes a detector for detecting the misregistration of the printing paper in the width direction thereof (which refers to a horizontal direction orthogonal to the longitudinal direction thereof hereinafter) for the purpose of controlling the position of ejection of inks toward the printing paper.
Such a conventional image recording apparatus including the detector is disclosed, for example, in Japanese Patent Application Laid-Open No. 2008-155628 and Japanese Patent Application Laid-Open No. 2003-182896. The apparatus disclosed in Japanese Patent Application Laid-Open No. 2008-155628 uses a plurality of line image sensors to detect the angle of skew of a recording medium, thereby adjusting the timing of ink ejection in accordance with the detected angle of skew (with reference to claims 1 and 2 and FIG. 1). The apparatus disclosed in Japanese Patent Application Laid-Open No. 2003-182896 includes two or more sensors for detecting edges of paper, and feeds a difference between outputs from the sensors where a constant time difference is established back to a corrector (with reference to claim 1 and FIG. 1).
Unfortunately, the image recording positions of the recording heads and the detection positions of the sensors are different on a transport path of the printing paper in the apparatuses disclosed in Japanese Patent Application Laid-Open No. 2008-155628 and Japanese Patent Application Laid-Open No. 2003-182896. In the configurations of these apparatuses, the widthwise positions of the printing paper in the respective recording positions accordingly do not precisely coincide with the detection results obtained from the respective sensors. For recording of an image of higher quality, it is necessary to identify the widthwise positions of the printing paper in the respective image recording positions. However, the recording heads are disposed in the respective recording positions of the printing paper. For this reason, it is often difficult in terms of space to place the sensors in addition to the recording heads in the respective recording positions. In particular, the space for the placement of the sensors is more limited in an apparatus which records an image across the full width of printing paper.
An apparatus disclosed in Japanese Patent Application Laid-Open No. 2016-88654 includes sensors disposed upstream and downstream of each recording position as seen in a transport direction, and calculates the widthwise position of printing paper in each recording position, based on the detection results from the sensors. This configuration is capable of predicting the widthwise position of the printing paper in each recording position without any detector disposed in each recording position. However, simple averaging of waveforms detected by the two sensors causes the amplitude of the resulting waveform to become smaller than the amplitude of the actual meandering waveform, as shown in FIG. 6 of Japanese Patent Application Laid-Open No. 2016-88654.